Internal combustion engine



Jan. 21, 1941. L. J. Ism-l:

'INTERNAL CQIBUSTION ENGINE 4 Sheets-Sheet 1 Filed latch ,15. 1938 Jan. 21, 1941.

l.` .1. ls'rAD INTER-NAL l COIIB'USTION ENGINE 4 Sheets-Sheet 2 Filed lax-ch 15. 1938 lNvENToR LARS J ISTAD mm ATTORNEY ina" jm. 2P., aar-*ein L, |$TAD ITERNL COHBUS'TION ENGINE Filed latch 15, 1938 4 Sheets-Sheet 3 lNvENToR LARS J, ISTAD Q BY WMU ATTQRNEY xm A .'Jan. 21, 1941. L J. ls'rAD INTERNAL COHBUSTION ENGINE Filed auch 15.11936 4 sheets-sheet 4 Patented Jan. 2l, 1941 UNITED STATES PATENT oFFicE INTERNAL COMBUSTION ENGINE Lars .1. Istad, Roselle Park, N. J.

Application March 15, 1938, Serial No. 195,951

zo claims. (ci. 12s-'58) rality of cylinders are arranged around a crank shaft parallel to each other and to the crank shaft, providing a compact construction of short transverse and longitudinal dimensions.

Another object of the invention is an improved fuel mixture and scavenging air controlling valve for engines generally but is especially applicable to engines in which the cylinders are arranged about the crank shaft.

Still another object of the invention is a simplified and improved construction for supercharging and scavenging the cylinders.

Among other objects of the invention are improved means for holding wabble plates against rotation, improved means for facilitating there-L moval of the wabble plates and their bushings from the crank shaft, and improved thrust bearings for receiving the thrust of the wabble plates as they are rocked by the operation of the pistons.

Other objects of the invention will appear from the following description taken in connection with thedrawings, in which:

Fig. 1 is a longitudinal vertical section through the engine block, taken substantially on the line I I Figs. 2 and 4;

Fig. 2 is a. composite view of transverse vertical y sections taken on the lines 2, 2A andl 2B of Fig. 1;

Fig. 3 is a section on the line 3 3 of Fig. 2;

Fig. 4 is a composite sectional view taken on the lines 4, 4A, 4B, 4C, of Fig. 1;

Fig. 5 is a side elevation of the valve;

Fig. 6 is a transverse vertical section on the line 6 6 of Fig. 5;

Fig. 7 is a transverse vertical section on the line 1 1 of Fig. 5;

Fig. 8 is a transverse vertical section on th line 8 8 of Fig. 5;

Fig. 9 is a transverse vertical section on theV Dall and socket connections Fig. 1 showing a valve adapted for use in a Diesel engine.

For the purposeA of disclosure I have illustrated a preferred form of my invention. The engine block'may comprise a main casting I5 provided with six cylinders I6, Fig. 4, extending from end to end of the casting and arranged around a central cylindrical opening I1, Fig. 1, in which is mounted a cylindrical extension I8 of a supplemental casting I9 provided with six cylinders 20 of larger diameter than that of cylinders I6, extending from end to end of this casting and in axial alinement with the cylinders i6 of the main casting I5. The' bores of the casting I9 and extension I 8 are preferably alined and have continuous walls. If desired the extension I8 may be made separate and extend into a bore in the casting I9. 'I'he castings I5 and I9 may be held together by rods 24 and nuts 25. Reduced extensionsv 26 on the rods 24 pass through end castings 21 and 28, and nuts 29 on the rods 24 secure the end castings 21 and 28 to the castings I5 and I9. A single casting may be used instead of the castings I5 and I9.

Mounted inside of the cylindrical extension I8 of the casting I9 and midway of the ends of the engine block is a short cylindrical member 30 provided with a bushing 3l, constituting the center bearing for a crank shaft 32. The center bearing member 30 may be held against rol tational 4and longitudinal movement with respect to the extension I8 by means of one or more bolts 33 as indicated.

The crank shaft 32 is provided with angular cranks 35 and 36 having their high portions adjacent the'center bearing 30, and with end bearing portions 31 and 38 which'rotate in bushings 39 and 46 supported in thrust members 4I and 42 -which are preferably pressed into tubular extensions 43 and 44 on theend castings 21 and 28. One endof the crank shaft may be provided with a fly wheel 45, and various mechanisms, such as the distributor and oil pump and so forth may be operated from this end of the shaft.

Mounted'within each of the cylinders I6 are pistons 50 and 5I. These 'pistons are connected by ball and socket connections with the piston rods 52 and 53 which in turn are connected by 54 and 55 with arms 56 and 51 of wabble plates 58 and 59. The wabble plates are provided with cylindrical bearing portions 60 and 6I surrounding the angular cranks 35 and 36. Two sets of spaced opposed semi-cylindrical exteriorly convexed bushspaced by a continuous cylindrical member 64, provided interiorly with concave cooperating surfaces. The parts are retained in place by a thrust ring 65 which is retained in place by a threaded retaining ring 66. The engaging cooperating faces of the thrust rings 65 and the thrust members 4| and 42 are frusto-conical with radial lines intersecting the angle between the axis of the adjacent crank and the axis of the end bearing of the crank shaft so that the wabble plate will roll on the thrust plates without any sliding movement between the engaging faces.

'Ihe pistons 5| in the right-hand ends of the cylinders I6 as shown in Fig. 1, control exhaust ports 1 0 through which the burnt gases are forced by scavenging air as will be described later. In the drawings I have applied to the ports, grooves, etc., the small letters a, sa, e, f and cf, to designate respectively, air, scavenging air, exhaust gases, fuel and compressed fuel.

The pistons 50 in the left-hand ends of the cylinders I6 Fig. l, control the scavenging ports 1|. Each piston has an enlarged portion or ilange 12 which operates in the cylinder 20 in the casting |9. 'Ihe flange 12 and piston 50, the wall of the cylinder 20, and the end of the casting I5 dene a super-charging chamber 13. The flange 12, the wall of the cylinder 20 and theclosed end 14 of the cylinder 20 define a scavenging chamber 15 into which scavenging air is drawn and compressed and then forced through a port 16 in the wall of the cylinder 20 and the port 1I into the cylinder I6 for the purpose of scavenging the cylinder of burnt gases. The closed end 14 of theV cylinder 20 comprises a cup-shaped member 11 provided with an annular slot 18 formed by a ange on said member and a. disk 19 secured thereto, to receive `an annulus on a. cup member 8| which together with a similar removable cup member 82 constitutes a socket for a two part ball member 83 through which the piston rod 52 operates, a sealing ring 84 being provided to effect an air tight seal between the ball 83 and thev rod I52. This construction closes the end 14 of the cylinder 20, forms an effective seal with the' piston rod 52, and permits reciprocating and angular movement of said rod.

The wabble plate 58 is held against rotation by sliding plates 85 Fig. 3 provided with sockets cooperating with the spherical end of the arm 56 and' which slide on tracks 86 supported upon extensions 81 projecting from the end wall of the casting 21. These tracks 86 are connected by a head 88 which constitutes the closure for the end wall of the casting. The casting 28 is alsoprovided with a. similar construction for preventing rotation of the' wabble plate 51. Neither has been vdisclosed in Fig. 1 as the former lies direcuy behind the parts s1, 4| and 43; and the latter directly behind the parts 38, 42 and 44. These` constructions arev preferably angularly alined; Suitable ignition mechanism may be employed and when the engine is used as a gas engine the spark plug may be located as shown in Fig. l. If the engine is used as a fuel oil engine the spark plug may be removed and replaced by a fuel oil spray injecting mechanism as is well understood.

. The walls of the cylinder 20 are also provided with scavenging air intake ports 90, ports `9| through which fuel mixture is sucked into the chamber 13 and through which it is ejected into ings 62 and 63 bear on the cranks and are held the space between the pistons 50 and 5| through ports 92 in the cylinder I6.

The casting I9 is provided with a scavengin air inlet 93 and a fuel mixture inlet 94. For the purpose of controlling the admission of the air and the fuel mixture into the various cylinders at the proper time, I have provided a single cylindrical valve 95 mounted in and having a clearance fit with the wall of the cylindrical opening in the casting I9. 'I'he wall of the Valve is thickened at 96 to provide a counter-weight for the crank 35 and is secured by three bolts 91 to a disc 98 secured to or integral with the crank shaft, the disc 98 fitting within the cylindrical opening in one end of the valve 95. The crank shaft is preferably provided with a senil-cylindrical member 99 to counter-balance the crank 36, and which is secured to an enlarged portion |00 on the crank shaft by three bolts |0I.

As disclosed in Fig. 5 the valve 95 is provided with a continuous groove |05 which is always in communication with the scavenging air intake 93. This groove which is shown in Figs. 7 and 14 communicates by means of a lateral port |06 with an interrupted groove |01, Fig. 6, through which scavenging air is sucked into the chamber 15 when it registers with the scavenging air intake port of this cylinder. 'I'he length of the groove |01 is such as to overlap several of the ports leading to the chambers 15. The inter- 'rupted' portion of the groove seals the chamber' 15 as the piston 50 moves towards the left so that the air sucked into the chamber'15 is compressed therein and i's forced out through the port 16 and through the port 1| when the latter has been uncovered by the piston 50, into the space between the pistons 50 and 5| and out through the exhaust ports 10 thereby scavenging the cylinder I6 of burnt gases.

registers with the port 9| communting with the chamber 13 on the forward side oi the flange 12 of the piston so that fuel is drawn into the chamber 13 as the ange 12 of the piston` 50 moves towards the left (Fig. 1). The communieating duct between the grooves 0 and ||I is shown by a broken line in Fig. 14.

The valve 95 is'also provided withan interrupted groove II2 Figs. 5 and 8, see also Fig. 14, which registers with the port 9| at the proper time during movement of the piston to the right, Fig. 1. 'I'his groove communicates witha short groove ||3 which registers with the port 92 in the cylindrical casting I8 and cylinder I6 at the proper time to provide a passage for the transfer of compressed fuel from the chamber 13 into.

the space betweenithe pistons`50 and 5| of the cylinder I6. 'I'he grooves ||0 and establish communication'between the fuel intake 94 and the chamber 13 and the grooves II2 and ||3 establish communication between the chamber 13 and the space between the pistons 50 and 5|. The groove II2 overlaps the ports 9| of several cylinders with the. result that the fuel cornpressed in the chamber 13 near the end of the stroke of the piston v5|) is transferred to the cylinder I6 with which the groove ||3 registers at that time.

By means of the construction shown the valve controls the admission of scavenging air into the chambers 15, the admission of fuel into the chambers i3 and the transfer of the compressed fuel from the chambers 13 into the cylinders I6. The same valve exercises the same control over the various cylinders in succession with the result that fuel will be drawn into the chambers 13 in succession and compressed therein in the same order and delivered into the cylinders I6 in the same order, and scavenging air will be drawn into the chambers 15 in succession and compressed therein in the same order. The pistons l control the exhaust ports 'Ill and the pistons 50 control the admission of fuel and scavenging air into the cylinders I5. Both the fuel and scavenging air are compressed when transferred into the cylinders it.

In Fig. I have shown the valve developed in a plane and also the ports in the cylinders I6 and 20 and on this and other figures have indicated the course taken by the scavenging air by the small letters a and sa, and e and the course taken by the fuel mixture by the small letters f and cf.

In the main disclosure I have shownA therighthand crank 36 in phase with the left-hand crank (Fig. 1) but in actual operation the crank 36 Will be located 20 degrees ahead of the crank 35 as indicated in Figs. l1, 12and 13.

I have described the engine as being a gas engine but it is obvious that the same could be used as afuel oil engine by replacing the spark plugs by oil spraying and injecting devices lili. In case the engine is used as a fuel oil engine, I may use a valve 95a provided with single groove H5 instead of the grooves |05 and il@ and ann air supply inlet Il@ instead of the vair and gas inlets 93 and 9G but otherwise the valve construction will be practically the same. The chamber H5 will be used for scavenging purposes as before and the chamber 'i3 will be used for forcing air under pressure into the space between the pistons and 5l for scavenging and/or super- Charging.

The semi-cylindrical bushings 62 and 53 which are convexed exteriorly together with the cylindrical member Slt, the end of the sleeves 53 and the thrust members @t which are complementarily concaved interiorly, constitute self alining bearings for the wabble plates whereby the thrust from the Wabble plates on the angular cranks will be uniformly distributed over a large area of the surface of the cranks.

By locating the angular or conical cranks as close to the center bearing as possible the overall length of the engine will be held to a minimum. This permits the wabble platesl to be mounted close to the ends of the main engine castings permitting the use of a relatively short crank shaft and relatively short piston rods and shallow end castings. Only a small additional space is required for mounting the valve in the position disclosed in the drawings, and the valve may be directly connected to the crank shaft thereby avoiding a train of valve actuating connections. This mounting of the valve also simplifies the construction of the inlet air and fuel mixture ports and the construction of the grooves of the valve which establish communication between said ports and the ports in the engine cylinder, and in the fuel mixture compression and scavenging air compression chambers. The cylindrical valve has an extended clearance't in the casting I9 and is wholly located within this casting providing for a compact construction and making it feasible to construct the valve as a single unit, and to arrange the grooves and inlivered n ot only to the associated engine cylinder but also to the next adjacent engine cylinder. The interrupted portion of the groove H3 prevents any of the exhaust or scavenging air from being forced back into the fuel mixture compression chambers or into the fuel line or into the adjacent engine cylinders. The groove H3 begins to register with the port 92 of a cylinder after the scavenging of that cylinder has been completed and is brought into full registry preferably'approximately as the scavenging air inlet port 'Il is -being closed by the piston 50 and Aafter the exhaust port 10 has been closed by the piston 5| thereby preventing any waste of fuel mixture.

As disclosed the exhaust port lli is opened before' the scavenging intake port Il is opened so that the cylinder may be scavenged freely immediately. upon opening of the port lli.

The phase relation of the cranks may be varied from that shown as may also the size and location of the various grooves and ports of the valve and cylinders. The crank shaft may be provided with lubricant distributing ducts through which a lubricant may be forced to the various bearings. Any suitable means may be provided for lubricating the valve and other movable parts. The center bearing 3d may, as shown, be provided With a groove and duct to prevent excess or used lubricant from reaching the valve. Instead of the wabble plates disclosed I may employ swash plates or other equivalents.

While I have described my invention with reference to a specific disclosure on the drawings, it is to be understood this is a preferred embodiment and that various changes may be made without departing from the spirit of my invention and that certain features disclosed may be applicable to other types of gas and fuel oil engines. It is also to be understood that the cylinder block may be made rotatable and mechanism may be driven from the rotating cylinder block in which case of course the crank shaft would -be held against rotation. Minor changes would be necessary to establish a connection between the fuel intake port 94 and the carburetor. Certain features are applicable to engines operated by iiuids under pressure and in broader aspects of my invention the valve may be indirectly operated by .the crank shaft or otherwise and may control more or fewer cylinders bearing a different relation to the crank shaft and in which the valve may be arranged variously with respect to the crank shaft and cylinders.

I claim:

1. The combination of an engine shaft, a cylinder block provided with a plurality of engine cylinders `arranged around and parallel tosaid shaft and provided with a cylindrical opening surrounding said shaft, angular cranks on said shaft, `opposed pistons within said cylinders, means for transferring movement from said pistons to said cranks, a cylindrical valve mounted in said cylindrical opening Within said block and surrounding one of said cranks, means connecting said valve to said shaft, said cylinders having ports for the admission of fuel, said block being provided with a fuel supply port, and said valve being provided with means cooperating with said ports for controlling the admission of fuel into said cylinders and means for exhaust.

2. The combination of an engine shaft, a cylinder block provided with a plurality of engine cylinders arranged around and parallel to said shaft and provided with a cylindrical opening surrounding said shaft, an angular crank on said shaft, pistons in said cylinders, means for transferring movement from said pistons to said crank, a cylindrical valve mounted in said cylindrical opening Within said block and surrounding said crank, and means connecting said valve to said shaft, said cylinders having ports for the admission of fuel, said block being provided with a fuel supply port, and said valve being provided with means cooperating with said ports for controlling the admission of Afuel into said, cylinders.

3. In combination with a two cycle engine comprising an engine shaft and a plurality of parallel cylinders spaced from and arranged concentrically about the engine shaft, a cylindrical valve seat Within the space d-ened by said cylinders and provided with a plurality of ports communicating with said cylinders, and a cylindrical valve surrounding and connected to said shaft and cooperating withsaid cylindrical seat, said valve being provided with a single port in constant communication with a source of fluid supply and adapted to be brought into registry serially with said ports.

4. In combination with an engine comprising an engine shaft and a plurality of parallel cylinders spaced from and arranged concentrically about the engine shaft, a cylindrical valve seat within the space defined by said cylinders and provided with a plurality of ports communicating with said cylinders, and a cylindrical valve surrounding and connected to said shaft and cooperating With said cylindrical seat, said valve being provided with a port in constant communii cationlwith a source of fluid supply adapted to be brought into registry serially with said ports, said port in said valve being of sumcient length to register simultaneously with a plurality of said ports.

5. In combination with a two cycle engine comvprising an engine shaft and a plurality of parallel cylinders spaced from and arranged concentrically about the engine shaft, a cylindrical valve seat within the space'deflned by said cylinders and provided with a fluid supply port and a plurality of ports communicating with said cylinders, and a cylindrical valve surrounding and connected to said shaft and cooperating with said cylindrical seat, said valve being provided with a single port in constant communication with said fluid supply port and adapted to be brought into registry serially with said ports communicating with said cylinders.

6. In combination with an engine comprising an engine shaft and a plurality of parallel cylinders .spaced from and arranged concentrically about the engine shaft, a cylindrical valve seat within the space defined by said cylinders provided with a fluid supply port and with a plurality of ports communicating with said cylinders, and a cylindrical valve surrounding and connected to said shaft and cooperating with said cylindrical seat,

, said valve being provided with a continuous groove in constant communication with said fluid supply port, and with an interrupted groove in communication with said. continuous groove and adapted to be brought into registry serially with said ports, said interrupted groove in said valve being of sufllcient length to register simultaneously with a plurality of said ports.

7. In an engine comprising an engine shaft and a series of engine cylinders arranged concentrically about the engine shaft and a series of fuel compression cylinders also arranged concentrically about said engine shaft, pistons in said engine and fuel compression cylinders operatively connected together and to said engine shaft, a cylindrical valve seat within the space defined by said cylinders, ported for communication with a source of fuel supply and with said fuel compression cylinders and also ported for the admission of compressed fuel from said fuel compression cylinders, into said engine cylinders, a cylindrical valve surrounding and operatively connected to` said engine shaft cooperating with said valve seat, said valve being provided with an interrupted groove in constant-communication with the fuel supply port and adapted to be brought into registry with the ports communieating with said fuel compression cylinders, said valve also being provided with' an interrupted groove adapted to be brought into communication with the ports communicating with said fuel compression cylinders and said engine cylinders.

8. In an engine comprising an engine shaft and a series of engine cylinders disposed concentrically about the engine shaft and a series of fuel compression chambers also arranged concentrically about said engine shaft, pistons in said engine and fuel compression cylinders operatively connected together and to said engine shaft, a cylindrical valve seat Within the space defined by said cylinders, ported for communication with a source of fuel supply and with said fuel compression cylinders and also ported for the admission of fuel into said engine cylinders, a cylindrical valve surrounding and operatively connected to said engine shaft cooperating with said valve seat, said valve being provided with an interrupted groove in constant communication with the fuel supply port and adapted to be brought into registry with the ports communicating with said compression cylinders, said valve also being provided with interrupted intercommunicating grooves adapted to be brought into registry with the ports communicating with said fuel compression cylinders and said engine cylinders, said first mentioned and said last mentioned interrupted grooves being disposed at opposite sides of said valve and said first mentioned groove adapted to be brought into registry with4 the ports in said compression cylinders being of a length to communicate with a plurality of said' ports leading into said compression cylinders simultaneously.

9. In an engine comprising an engine shaft and a series of groups of cylinders disposed concentrically with respect to said engine shaft, eachsaid cylindrical seat, said seat being also ported,"

to establish communication with a source of fuel supply and the atmosphere, said valve being provided with an interrupted groove in constant communication with the port leading to the 5 atmosphere and adapted to register with the ports communicating with the scavenging air compression cylinders, said valve also being provided with an interrupted groove in constant communication with a fuel supply port and adapted l to be brought into registration with the ports 'communicating with the fuel compression cylinders, said valve also being provided with interrupted grooves adapted to be brought into registration with the ports leading to said engine 15 cylinders and the ports communicating'with said fuel compression cylinders.

10. In an engine comprising an engine shaft and a series of groups of cylinders disposed concentrically with respect to the engine shaft, each 20 group of cylinders comprising an engine cylinder, a fuel compression cylinder and a scavenging air compression cylinder, vpiston means operating in said cylinders and` operatively connected together and to said engine shaft, a cy- 25 lindrical valve seat disposed Within said groups of cylinders ported for communication with said cylinders, a cylindrical valve surrounding and operatively connected to said engine shaft and n cooperating with said cylindrical seat, said seat 30 being also ported to establish communication with a source of fuel supply and the atmosphere,

said valve being provided with an interrupted groove in constant communication with the port leading to the atmosphere and adapted to reg- 35 ister with the ports vcommunicating with the scavenging air compression cylinders, said Valve also being provided with an interrupted groove in constant communication with said fuel supply port and adapted to be brought into registra- 49 tion with the ports communicating with the fuel compression cylinders, said valve also being provided With interrupted intercommunicating grooves adapted to be brought into registration with the ports leading to said engine cylinders g5-and with the ports communicating with said fuel compression chamber, said interrupted grooves cooperating with the ports in said scavenging air and fuel compression chambers being of a length to register simultaneously with a plurality of said 50 ports.

11. A cylindrical valve having an exterior cylindrical valve face provided with circumferentially continuous and interrupted intercommunicating grooves and intercommunicating inter- 55 rupted grooves located diametrically opposite saidfirst mentioned interrupted groove with one of said latter interrupted grooves in the same plane as said first mentioned interrupted groove` 12. A cylindrical valve having an exterior cyo lindric'al valve face provided with circumferentially continuous and interrupted intercommunicating grooves and intercommunicating interrupted grooves located diametrically opposite said flrst mentioned interrupted groove withv one 65 of said latter interrupted grooves `in the same plane as said first mentioned interrupted grooves, the .other of said second mentioned interrupted grooves being of a length to communicate serially individually with ports and said interrupted 70 grooves located in the same plane being of -a length to communicate serially with a plurality of ports simultaneously. y

13. The combination in ang/engine of an engine shaft, a plurality of scavenging air compresi cien cylinders and a plurality of engine cylinders,

pistons in corresponding scavenging and engine cylinders operatively interconnected and operatively connected to said engine shaft, said cylinders being provided with inlet ports, and a single valve element operatively connected to said shaft for 4controlling the admission of` fluid into said cylinders in proper timed relation, said corresponding scavenging air compression and engine cylinders being provided with intercommunicating ports for transferring compressed scavenging -air directly from the former to the latter, said latter ports in said engine cylinders being controlled by the pistons in said engine cylinders.

14. The combination in an engine of an engine shaft, a plurality of fuel compression and engine cylinders, pistons operating in lsaid cylinders operatively interconnected and operatively connected to said engine shaft, each fuel compression cylinder being provided with a port for the admission and expulsion of fuel and each engine cylinder being provided with a port for the admission of fuel, and a single valve operatively connected to said engine shaft operating to control the admission of fuel into said fuel cornpression cylinders and transfer of compressed fuel from said fuel compression cylinders into said engine cylinders.

15. 'Ihe combination of an engine shaft, a plurality of engine cylinders arranged about said shaft in spaced concentric relation thereto, a crank on said shaft located within the connes of said cylinders, said cylinders being provided with ports, and a valve for controllingesaid ports operatively connected-to said shaft and surrounding said crank and weighted to counterbalance said crank, said valve provided with a thickened portion having an eccentrically located hole therein, a projection on said shaft also provided with an eccentrically located hole to cooperate with said hole in said thickened portion of the 0 valve, and means through said cooperating holes securing said thickened portion of said Valve to said projection on the shaft.

16. The combination in an engine, of an engine shaft, a plurality of engine cylinders, pisa 5 tons in said cylinders operatively connected to said shaft, said cylinders being provided With fuel linlet ports, positioned to be unmasked by the respective pistons during the out-stroke of the pistons, and a single valve element for preventing flow of gases of explosion through said ports as they are unmasked by the pistons during their out-stroke yand for admitting fuel to said ports during the in-stroke of the pistons While the ports remain unmasked by said pistons.

17. The combination in an engine, of an engine shaft, a plurality of engine cylinders, pistons in said cylinders operatively connected to said shaft, said cylinders being provided with fuel inlet ports and scavenging air inlet ports adapted 00 -to be unmasked by said pistons in the order stated during the out-stroke of the pistons, and a single valve operating to connect said fuel inlet ports with a source of fuel supply during the instrokes of the pistons after the pistons have masked the scavenging air inlets and to disconnect said source of fuel supply from said fuel inlet ports to prevent exploded gases and scavenging air from entering said source of fuel supply during the outstroke and unmasking of the fuel inlet ports by .said pistons.

18. An engine comprising a series of cylinders including a combustion cylinder, an over-compression cylinder and a scavenging cylinder, in-

terconnected pistonsin said cylinders, said scavf enging and combustion cylinders being provided with interconnected ports and said over-compression cylinder and combustion cylinder being provided with interconnected ports, said ports in said combustion cylinder being located near the outer end of the cylinder and so relatively arranged -that the port admitting uid from the over-compression cylinder is opened by the piston in the combustion cylinder before the port admitting iiuid from the scavenging cylinder is opened during the outward stroke oi the piston, and a valve controlling the admission of fluid into the scavenging and over-compression cylinders and from the over-compression'cylinder into the combustion cylinder, said valve operating to interrupt communication between the interconnected ports connecting the over-compression cylinder to the combustion cylinder during the outward stroke oi' the piston and to connect said ports during the inward stroke of the piston after the port admitting scavenging air into the combustion cylinder has been closed by the piston during its inward stroke.

19. An engine comprising a series of cylinders including a combustion cylinderan over-compression cylinder and a scavenging cylinder, interconnected pistons in said cylinders, said scavenging and combustion cylinders being provided with interconnected ports and said over-compression cylinder and combustion cylinder being provided with interconnected ports, said ports in said combustion cylinder being located near the outer end of the cylinder and so relatively arranged that the portadmitting fluid from the v over-compression cylinder is opened by the piston in the combustion cylinder before the port admitting fluid from the scavenging cylinder is opened during the outward stroke of the piston, a valve controlling the admission of' iluid into the scavenging and over-compression cylinders and from the over-compression cylinder into the combustion cylinder, said valve operating to interrupt communication between the interconnected ports connecting the over-compression cylinder to the combustion'cylinder during the outward stroke of the piston and to connect said ports during the inward stroke of the piston after the port admitting scavenging air into the combustion cylinder has been closed by the plston during its inward stroke, an opposed piston mounted in said combustion cylinder, an engineshaft, and connections between said pistons and said engine shaft, said pistons moving in opposite directions and said combustion cylinder being provided with exhaust ports' adapted to be uncovered by said last mentioned piston during its outward stroke and to be covered by said piston substantially at the time that masking of the scavenging port has been effected by the other piston in the combustion cylinder and admission of over-compressed fluid into the combustion cylinder from said over-compression cylinder is started under control of the valve.

20. In a barrel type engine comprising a cylinder block, said block having a plurality of cylinders arranged in a circle along the vouter periphery of the block and being all parallel to the axis of the block, said blo'ck also having a central cylindrical space coaxial with the block and forming a cylindrical valve seat; a crank shaft journaled at the axis of said cylinder block; a pair of opposed pistons in each of said cylinders, the cylinders and pistons at one end of the block being of the stepped type and providing supercharging chambers between the larger diameter parts of the pistons and the cylinder block; closures iltted in the ends of the stepped cylinders having the stepped pistons thereby forming scavenging chambers between said closure and the larger diameter part of the stepped piston; means for transferring the linear motion of the said pistons to a rotational motion of said crank shaft; a cylindrical valve located in said valve seat and rotatable by said crank shaft, said valve being circumferentially grooved, intake means communicating with the grooves of said valve, and said block being provided with inlet ports communicating with said supercharging and scavenging chambers and controlled by said valve and inlet ports communicating with the explosion chambers oi." the cylinders and governedby the coordinated operation of said pis: tons and cylindrical valve.

LARS J. ISTAD. 

